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(N0 Model.) J METHOD OF AND APPARATUS P RANSFO NG ALTERNATING INTOGONTIN OURRE No. 522,988. Patented July 17, 1894."

J? v w UNITED STATES PATENT EEICE.

JOHN F. KELLY, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO THE STANLEYLABORATORY COMPANY, OF SAME PLACE.

METHOD OF AND APPARATUS FOR TRANSFORMING ALTERNATING INTO CONTINUOUSCURRENTS.

SPECIFICATION forming part of Letters Patent No. 522,988, dated July 17,1 894.

Application filed January 6, 1894. Serial No. 495,930- (No model.)

To a/ZZ whom it may concern:

Be it known that 1, JOHN F. KELLY, a citizen of the UnitedStates,residing at Pittsfield, in the county of Berkshire and State ofMassachusetts, have invented certain newand useful Improvements inMethods of and Apparatus for Transforming Alternating into ContinuousCurrents, of which the following is a specification, reference being hadto the drawings accompanying and forming a part of the same.

The alternating electro-motive force produced by such generators as arecommonly used, varies as the sine of the angle traversed, that is tosay, it is proportionate at any given instant to the sine of the anglethrough which the induced coil has passed from the zero or startingpoint, the angle between two similar poles being considered as equal tofour right angles, or 27: and corresponds in form to the curve expressedby the value E sin 27mt, in which E is the maximum electromotive force,at the number of complete cycles, or revolutions of the coil per second,25 the time at any instant required by the coil to reach a given point,measured from the beginning of a cycle and hence variable, and 7: thesymbol for the ratio between diameter and circumference. Of two suchelectro-motive forces, therefore, in quadrature, or which have a fixeddisplacement of ninety degrees, one will vary as the sine and the otheras the cosine of the angle 27:12.25 for all its values. Various methodsand appliances have been proposed for commuting and adding together twosuch electro-motive forces to produce a unidirectional current, but theresulting current will of necessity undergo a very considerablevariation in electro-motive force, since it may be readily shown that ifthe two added electro-motive forces vary respectively as the sine andcosine of the same angles,at times their sum exceeds the maximum valueof either. If, however, they be compelled to vary respectively as thesine squared and cosine squared of the angle traversed, their sum willalways be constant, and the object of my invention is to effect thisresult in a novel and simple manner.

As I may illustrate most readily the nature of my invention by adiagram, I now refer to the accompanying drawings.

Figures 1 to 9 are diagrams illustrative of the principle of theinvention. Fig. 10 is a diagrammatic illustration of a device forming apart of the mechanism for practically carrying out the invention. Fig.11 is a similar illustration of a complete combination ofdevices of theinvention.

Let it be assumed that two points, A, B, Figs. 1 to 9, are connected bya uniform conductor D and that an alternating electro-motive force ismaintained between them which varies as the sine of the angle traversed,or is of the form E sin 2am. Let X Y represent two brushes in contactwith such conductor and assume that at the instant when E sin 27mt: 0,both brushes are at the point A, with brush Y just about to start towardB at a velocity: A B cos 21mt, or in other words, so that the distancebetween the brushes at any instant of time will be proportionate to thesine of the angle 2711275. If now we assume that the electro-motiveforce between the brushes will be to the distance between them as thisdistance is to the distance A B,which would be the case if we assumethat the current drawn off by the brushes is not sufficient to disturbthe distribution of the electro-motive forces, it is obvious that theelectro-motive force between the brushes will be equal at anyinstantuntil B is reachedto that at the terminals A B multiplied by the ratioof the distance between the brushes and the distance A B, that is, itwill be equal to E sin 27mt.

Under the conditions assumed, the position of the brush Y at the end ofthe first eighth of a period would be at a point about seventenths ofthe total distance from A to B, as

shown in Fig. 3, so that it would be receiving only a fractional part ofthe electro-motive force at that point, while at the end of the firstquarter of a period it will have reached the point B. The curve of thecurrent which the brushes'have thus drawn off will rise as the sinesquared of the angle traversed.

If when brush Y reaches B it be caused to return over the same path atthe same rate, we shall have the same law for the electromotive force inthe second quadrant, the current drawn off falling to zero, when the twobrushes are again at A, and the electro-motive force between A and Bbeing zero and about to become negative. Let us now start brush X overthe path toward B at the same rate as before. The electro-motive forcebetween the brushes will evidently follow the same law as to magnitudeas before, and the position of the brushes with respect to A, B, havingchanged when the electro-moti ve force between A and B changed sign, itis evident that the electro-motive force between the brushes will be ofthe same sign as before. WVhen X reaches 13 it stops and then returns,following the same law as to velocity. If new we assume another similarconductor-between the terminals of which is maintained an electro-motiveforce of the form E cos 271m, and along which the brushes are similarlymoved with the velocity A B sin 27mt, or so that, as before, thedistance between the brushes at any instant of time will beproportionate to the cosine of the angle 271ml, the brushes being atopposite ends of the conductor at starting, it is obvious that we willhave between this second pair of brushes an electro-motive force whichwill vary as the cosine squared of the angle traversed. If therefore, weconnect the two sets of brushes together so as to superimpose the twoelectro-motive forces, we shall have a resultant electro-motive force ofthe form E (sin Zfint-l-cos 2am), which for all values of t is constantand equal to E, or unity.

Since the rectilinear movement of the brushes in the illustrative caseabove is not uniform, it would be difficult in practice to secure itproperly, but the same result may be attained in a simple andpracticable way by means of such a mechanism as l have illustrated inFigs. 10 and 11.

The conductor D, Fig. 10, is in the form of a coil, such as thesecondary of a transformer, a self-induction coil, the induced coil of adynamo or the like. If this conductor be divided up into a certainnumber of sections of proper lengths and a brush caused to travel at auniform rate in contact with the terminals of such sections, it isevident that the proportionate part of such conductor included betweensuch brush and a stationary brush connected with one end of theconductor will depend upon the relative lengths of the sections. 1therefore proportion these sections in the following manner: Supposethat there are M sections in the conductor, and that the whole number ofturns or length of the conductor which we will represent by Lbe taken ascorresponding to the sin j vr or ninety degrees. Then the number ofturns included in the first section beginning with the largest will besin S L the number included in the first two sections, sin l), in thefirst three e and a, b, c, d, c, and a continuous plate f so arrangedthat two brushes 72', may be caused to sweep over them, the dispositionof the plates being such that during one half of the cycle of movementone brush, as h, will remain in contact with f, while brush 7c passessuccessively over plates at, b, c, d, c, and during the remaining timethe brush 7; remains in contact with f' while brush 7L passessuecessively over plates a, b, 0, cl, c.

Any well known disposition or arrangement of parts may be followed insecuring the result, but for simplicity, I have shown the plates assecured to a flat surface in two eoncentric circles, one half of eachbeing composed of the plates at, I), e, (Z, c and d, Z), c, d, 6respectively and the other half by the platef, the two parts of whichare electrically connected.

F is an arm carrying the two brushes h, 7; and motion is imparted to itso that the brushes make one complete revolution in the time occupied bya complete cycle of the current to be transformed.

One terminal of the conductor D is connected with platef and theterminals of the several sections are connected in order to plates a, b,and c. It, therefore, the brush 7. be caused to traverse in successionthe contacts a, b, c in a quarter period, brush 71, meanwhile remainingon plate f, all of the conductor D will have been traversed in thattime, the number of turns included in the air cuit varying as abovedescribed so that the electro-motive force between the brushes 7t and 70will be equal, at any instant, to E sin 27rnt. If the brushes be thenmoved back the sections of conductor D will be cut out in re verseorder, but this is more readily accom plished by causing the brushes tocontinue their motion so that brush 7:; passes over plates 0, d, 6 whilebrush 7L remains 011 platef, said plates d and (2 being connected withthe sections of D but in the opposite order to a and I), so that aforward motion of brush 7.; from c to c is equivalent to a backwardmotion from c to C6. The two brushes being carried around together onein contact with the continuous platef, pass from the point A, when theyinclude no section to B, where they include all the sections ofconductor D,and thence to A, where they again include no section.

At A, the continuous plate and the sections change places with referenceto the brushes, so that the brushes in traveling onward reverse theconnections of the conductor with respect to the external circuit.

The order of the plates at, h, c is also reversed again in the thirdquadrant so that the last section of D cut out in the second quadrant isthe first brought in in the third, and it will be understood that theplates in the third quadrant are connected in the same order as those inthe first, while those in the fourth quadrant are connected in the sameorder as those in the second.

As the pair of brushes are rotated synchro' nously with the impressedfrequency, they will include between them a number of turnssubstantially proportioned to the sine of the angle of rotation, and asthe electro-motive force at the terminals of the conductor D is alsovarying as the sine of the same angle, the electro-moti've force betweenthe brushes will be substantially proportional to the square of thesine.

A similar conductor D and a commutator such as described, but with thephase of the electro-motive force shifted ninety degrees, will give anelectro-motive force substantially proportional to the square of thecosine, and if we-connect the two sets of brushes so as to superimposethe two electro-motive forces their sum will be constant. This isillustrated in Fig. 11, where V, W, indicate the leads from a source oftwo alternating currents in quadrature and R the common return. P and Pare the primaries of transformers included in the two circuitsrespectively and D, D the secondaries, connected with the commutators asabove described.

I have shown a small synchronous motor S for rotating the brushes andhave indicated the external circuit into which the corrected currentsare delivered by T.

It will be understood from the nature of the case that the conductor Dshould have a high self-induction in order to avoid loss of energy.

The mechanical construction and arrangement of the mechanism forcarrying out my invention may be greatly modified. In this, as inanalogous classes of mechanism, it is immaterial to the character of theultimate result, for example, whether the commutator or the brushesrevolve, or whetherthe commutator be arranged on a flat or on acylindrical surface. My invention is not, however, limited to thespecific devices herein described. It will also be understood that thenumber of sections into which the conductor D is divided should ingeneral be greater than shown herein for purposes of illustration.

In illustration of the invention and the way in which the same is or maybe carried into efiect, I have confined the description to the case oftwo alternating currents in quadrature, but the same principles apply tothe transformation of any number of currents between which there existsa uniform difference in phase. For if we represent the difference inphase by a, we may write for a multiphase system of electromotiveforces, E sin (271m), E sin (27mzH-a), E sin (27mt-l-2a) E sin (27mt-l-(qt-4) a), and then the length of conductor or number of turns includedin each coil of the device described will vary as sin (271m), sin(27mt-l-a), &c., respectively, or what is the same-thing, the rate ofmotion of the brushes will vary as the cosines of the said angles. Theelectromotive forces between the various pairs of brushes will then berespectively E sin 27m,- E sin (2vmt-l-a); E sin (27mt-l-2a) E sin(27mt+(n-1) a).

The sum of this series is independent of t whatever the value of .n.

When there are only two currents in quadrature, we have'for theelectro-motive forces E sin (271m), and E sin (2mtt-l-a) and abeing 17:now equal to ninety degrees or these exelectro-motive forces and numberof turns in circuit must be expressed as functions of the sines of theseveral variable angles, and the rate of motion of the brushes asfunctions of the cosines of the same angles respectively.

It will be observed that if a unidirectional current be supplied to therotating brushes that the converse of the operation takes place and thatmulti-phase currents would be produced in the conductors.

Having now described my invention, what I claim is- 1. The method oftransforming a plurality of alternating currents of the same frequencyand uniform phase difference into a unidirectional current ofsubstantially constant electro-motive force, which consists incollecting such fractional portions of the electro-motive forces asshall vary as the sines squared of the current phases and superimposingthe same as herein set forth.

2. The electrical transformer herein de-' scribed comprising incombination a conductor adapted for connection with a source ofalternating current which varies as the sine of the angle traversed byits inducing conductor, collecting brushes movable along said conductorin alternately opposite directions and means for moving said brushes insynchronism with the frequency of the current and at a rateproportionate to the cosine of the angle traversed by its inducingconductor, as set forth.

3. The combination with a conductor traversed by or adapted to carry analternating current which varies as the sine of the angle traversed byits inducing conductor of the following devices, viz: a circularseriesof contact plates, comprising four groups, the plates of each groupbeing connected in alternately reversed order to the conductor at suchdistances apart that the amount of said conductor included in any numberof sections taken from the end next the largest is to the wholeconductor as the sine of 8.1416 times the number of sections considereddivided by twice the total number of sections is to unity, a continuouscontact connected with one terminal of the conductor, a pair of rotarybrushes alternately bearing on the continuous and sectional contactsduring each successive half revolution, and means for rotating saidbrushes synchronously with the frequency of the current, as hereindescribed.

4. The electrical transformer herein described comprising in combinationtwo conductors adapted for connection with sources of alternatingcurrents which vary as the sine and cosine of the same angles,collecting brushes movable along said conductors in alternately oppositedirections and means for moving said brushes in synchronism with thefrequency of the currents and at a rate proportionate respectively tothe cosine and sine of the angles traversed by the inducing coils of thegenerator and connections between the brushes whereby the currentscollected and commuted by them will be superimposed, as set forth.

5. The combination with each of two conductors traversed by or adaptedto carry two alternating currents which vary as the sine and cosine ofthe same angles, of the following devices, viz., a circular series ofcontact plates, comprising four groups, the plates of each group beingconnectedin alternately reversed order to the conductor at suchdistances apart that the amount included in any number of sectionscounting from the end next the largest is to the whole conductor as thesine of 3.1416 times the number of sections considered divided by twicethe whole number of sections is to unity, a continuous contact connectedwith one terminal of the conductor, a pair of rotating brushesalternately bearing on the continuous and sectional contacts during eachsuccessive half revolution, means for rotating such brushessynchronously with the frequency of the current and connections betweenthe brushes whereby the currents collected and commuted by the same willbe superimposed, as set forth.

6. The combination with an alternate current coil 1), divided intosections, the number of turns of each being such that the amountincluded in any numberof sections counting from the end next the largestis to the whole conductor as the sine of 3.14116 times the num ber ofsections considered divided by twice the whole number of sections is tounity, of a series of contact plates forming the terminals of saidsections, a continuous contact plate f, brushes h, 70, means for movingsaid brushes over said plates so as to collect a uni-directional currentvarying as the sine squared of the angle traversed by the inducing coilof the generator, a second conductor, and commutator similar to thefirst but delivering an electro-motive force varying as the cosinesquared of the angle, traversed by the said inducing coil andconnections between the two sets of brushes whereby the two currents aresuperimposed, as set forth.

7. The combination with two sources of alternating currents which varyrespectively as the sine and cosine of the same angles,of two conductorsor coils connected to the said sources, means for collecting from saidcoils alternating electro-motive forces Varying as the sine squared andcosine squared of the same angles, commutators for correcting orstraightening such currents and electrical connections for combiningthem into a single current, as set forth.

JOHN F. KELLY.

"Witnesses:

\VILLIAM STANLY, J r., E. L. FRENCH.

